This invention relates to a testing device for evaluating the immunity of an electronic device to electromagnetic noise, such as electrical transients, power interruptions and Radio Frequency Interference (RFI).
Electronic devices may be susceptible to a wide variety of electromagnetic noise. Electromagnetic noise includes electrical transients, power interruptions and RFI that may be radiated or conducted by man-made equipment such as electrical equipment or machinery. For example, electromagnetic noise may be created if a machine has an electric motor that is turned on via an electromechanical switch. The electric motor has windings, which form an inductive load. The inductive load may cause electrical transients or power interruptions on power transmission lines that are coupled to an electronic device. In the case of an automobile electrical system, a windshield wiper motor or an electric fuel pump can induce electrical transients into the electrical system which may interfere with other more sensitive electronic devices, such as a radio or a compact disc player.
Electronic devices, such as radios or microprocessor-based equipment, may be susceptible to RFI from cellular phones, citizen band radios, and other transmitting equipment. For example, an engine control module may be exposed to radiation from a land mobile transmitter installed on the vehicle, which may result in reduced performance due to interference with the engine control module.
Electronics manufacturers may use tests with expensive test equipment to identify potential susceptibility or a lack of immunity of an electronic device to electromagnetic noise. For example, an automotive electronics manufacturer may use a standardized test, consistent with International Standards Organization (ISO) 7637 or another applicable standard, to test electronic equipment for immunity to electrical or electromagnetic noise. Standard tests may require a high level of technical skill and expertise in electrical and electronic testing. In addition, standard tests involve the expense of purchasing and maintaining the equipment that may be required to conduct the test according to the specified guidelines or requirements.
Even if an electronic device complies with a standardized test of immunity to electromagnetic interference, the actual performance of the electronic device in the field may be deficient in the presence of electromagnetic interference. If immunity problems are not identified sufficiently early in the design of the electronic device, then the quality and performance of the electronic device may suffer. Further, the expense of any remedial or corrective action of the design of the electronic device may be substantially increased as a design matures or is introduced into actual production.
Commercially available test equipment may be used to generate repeatable electromagnetic noise with a precise amplitude and spectral response. However, arranging the commercial test equipment to scan over a wide spectrum with different amplitudes may be necessary to identify deficient performance of certain microprocessor-based equipment. Many commercially available transient noise generators require an inordinate amount of testing time to align or match the characteristics of the electromagnetic noise to the susceptible portion of executable software of microprocessor-based equipment.
Thus, a need exists for an inexpensive, easy-to-use testing device and procedure that can effectively identify or screen potential realistic field concerns associated with electronic equipment. Further, a need exists for a testing device that facilitates the optimization of the design of the electronic equipment.
In accordance with the invention, a testing device generates electromagnetic noise for application to an electronic device to easily evaluate the immunity of the electronic device to electromagnetic noise or to test the performance of the electronic device during exposure to electromagnetic noise. The testing device includes a switch having electrical contacts for producing electromagnetic noise during a transition between a closed state and an open state of the electrical contacts. A trigger is coupled to the switch. The trigger is arranged to change states of the switch between the closed state and the open state of the electrical contacts. An input terminal is associated with the switch for applying electrical energy to the switch. An output terminal is associated with the switch for connection to an input terminal of the electronic device for testing operation of the electronic device in response to the electromagnetic noise.
In accordance with one aspect of the invention, the testing device may include a resistive arrangement (e.g., a potentiometer) for adjusting the level of electromagnetic noise applied to the tested device. For example, the resistive arrangement may permit the level of electromagnetic noise applied to the test device to be adjusted to mimic real world conditions present in a vehicular or automotive environment. The testing device of the invention is well suited for use by non-experts and does not require elaborate training or expertise for reliable test results.
In accordance with another aspect of the invention, the testing device may include a resistive network coupled to the output terminal of the switch. The resistive network allows coupling of electromagnetic noise to the electronic device. Various combinations of the resistive network, the trigger, and input electrical energy allow different magnitudes or other characteristics of electromagnetic noise to be generated.